Subject: Re: README: kernel pty struct allocation change
To: Jarommr Dolehek <>
From: Andrew Gillham <>
List: current-users
Date: 09/09/2000 18:56:35
Jarommr Dolehek writes:
> now does not mean that the fixed number is available, but rather
> how big is the array of pointers to pty structs on the start.
> If 'foo' is not given, 64 is used. This initial array is enlarged
> as necessary.
> There is now new sysctl kern.maxptys, which limits how many maximum
> pty's might exist.  This defaults to 512. This limit can only be
> raised.  Note you need to install newer kernel includes and rebuild
> sysctl(8) for it to support this new sysctl.

What is the upper limit on this value?  How many ptys can be expected
to work correctly considering the kernel memory and /dev filenames?
Looking at MAKEDEV (on i386) it appears that only 240 can be addressed?

Would it be reasonable to expect to be able to have 512 people logged in
at one time?  Can NetBSD support thousands of concurrent logins?
Don't some of the commercial unixes (Solaris?) support >= 2048 concurrent

Not that I would expect to need so many, but is there an upper limit?
What about the 'maxusers' kernel option?  Will it scale so far?
I'm mostly curious from the perspective of allocating ptys as needed and
finding out at 295 (arbitrary number) that kernel memory is exhausted, etc.

Thanks for any insight.